Bronchial pathology in chronic marijuana smokers: a light and electron microscopic study

Modulation of pulmonary immune function by inhaled cannabis products and consequences for lung disease

The lungs, in addition to participating in gas exchange, represent the first line of defense against inhaled pathogens and respiratory toxicants. Cells lining the airways and alveoli include epithelial cells and alveolar macrophages, the latter being resident innate immune cells important in surfactant recycling, protection against bacterial invasion and modulation of lung immune homeostasis. Environmental exposure to toxicants found in cigarette smoke, air pollution and cannabis can alter the number and function of immune cells in the lungs. Cannabis (marijuana) is a plant-derived product that is typically inhaled in the form of smoke from a joint. However, alternative delivery methods such as vaping, which heats the plant without combustion, are becoming more common. Cannabis use has increased in recent years, coinciding with more countries legalizing cannabis for both recreational and medicinal purposes. Cannabis may have numerous health benefits owing to the presence of cannabinoids that dampen immune function and therefore tame inflammation that is associated with chronic diseases such as arthritis. The health effects that could come with cannabis use remain poorly understood, particularly inhaled cannabis products that may directly impact the pulmonary immune system. Herein, we first describe the bioactive phytochemicals present in cannabis, with an emphasis on cannabinoids and their ability to interact with the endocannabinoid system. We also review the current state-of-knowledge as to how inhaled cannabis/cannabinoids can shape immune response in the lungs and discuss the potential consequences of altered pulmonary immunity. Overall, more research is needed to understand how cannabis inhalation shapes the pulmonary immune response to balance physiological and beneficial responses with potential deleterious consequences on the lungs.

Pulmonary effects of inhaled cannabis smoke

Background: The smoke generated from cannabis delivers biologically active cannabinoids and a number of combustion-derived toxins, both of which raise questions regarding the impact of cannabis smoking on lung function, airway inflammation and smoking-related lung disease.Objectives: Review the potential effects of cannabis smoking on respiratory symptoms, lung function, histologic/molecular alterations in the bronchial mucosa, smoking-related changes in alveolar macrophage function and the potential clinical impact of cannabis smoking on chronic obstructive pulmonary disease, lung cancer and pulmonary infections.Methods: Focused literature review.Results: The carcinogens and respiratory toxins in cannabis and tobacco smoke are similar but the smoking topography for cannabis results in higher per-puff exposures to inhaled tar and gases. The frequency of chronic cough, sputum and wheeze and the presence of airway mucosal inflammation, goblet cell and vascular hyperplasia, metaplasia and cellular disorganization are similar between cannabis smokers and tobacco smokers. Cannabis smoke has modest airway bronchodilator properties but of unclear clinical significance. While clear evidence exists for progression to obstructive lung disease and emphysema in chronic tobacco smokers, the effects from habitual cannabis use are less clear. Evidence suggests that alveolar macrophages from cannabis smokers have deficits in cytokine production and antimicrobial activity not present in cells from tobacco smokers.Conclusions: Solid conclusions regarding the respiratory consequences of regular cannabis smoking are difficult to make due to a relative paucity of literature, confounding by concurrent tobacco smoking and reports of conflicting outcomes. Additional well-controlled clinical studies on the pulmonary consequences of habitual cannabis use are needed.

Cannabis smoking and respiratory health: consideration of the literature

The respiratory health effects from tobacco smoking are well described. Cannabis smoke contains a similar profile of carcinogenic chemicals as tobacco smoke but is inhaled more deeply. Although cannabis smoke is known to contain similar harmful and carcinogenic substances to tobacco smoke, relatively little is understood regarding the respiratory health effects from cannabis smoking. There is a need to integrate research on cannabis and respiratory health effects so that gaps in the literature can be identified and the more consistent findings can be consolidated with the purpose of educating smokers and health service providers. This review focuses on several aspects of respiratory health and cannabis use (as well as concurrent cannabis and tobacco use) and provides an update to (i) the pathophysiology; (ii) general respiratory health including symptoms of chronic bronchitis; and (iii) lung cancer.

Cannabis use and cancer of the head and neck: case-control study

Objective

To investigate whether cannabis smoking increases the risk of head and neck cancer.

Design

Case-control study.

Subjects and Methods

Cases of head and neck cancer ≤55 years identified from hospital databases and the Cancer Registry, and controls randomly selected from the electoral roll completed interviewer-administered questionnaires. Logistic regression was used to estimate the relative risk of head and neck cancer.

Results

There were 75 cases and 319 controls. An increased risk of cancer was found with increasing tobacco use, alcohol consumption, and decreased income but not increasing cannabis use. The highest tertile of cannabis use (>8.3 joint years) was associated with a nonsignificant increased risk of cancer (relative risk = 1.6, 95% confidence interval, 0.5-5.2) after adjustment for confounding variables.

Conclusions

Cannabis use did not increase the risk of head and neck cancer; however, because of the limited power and duration of use studied, a small or longer-term effect cannot be excluded.

Marijuana Use and Risk of Oral Squamous Cell Carcinoma

Previous laboratory investigations, case reports, and a hospital-based case-control study have suggested that marijuana use may be a risk factor for squamous cell head and neck cancer. We conducted a population-based case-control study to determine whether marijuana use is associated with the development of oral squamous cell carcinoma (OSCC). Case subjects (n = 407) were 18-65-year-old residents of three counties in western Washington State who were newly diagnosed with OSCC from 1985 through 1995. Control subjects (n = 615), who were similar to the cases with respect to age and sex, were selected from the general population using random-digit telephone dialing. Lifetime histories of marijuana use and exposure to known OSCC risk factors were ascertained using a structured questionnaire. Information on genetic polymorphisms in glutathione S-transferase enzymes was obtained from assays on participant DNA. Odds ratios for associations with features of marijuana use were adjusted for sex, education, birth year, alcohol consumption, and cigarette smoking. A similar proportion of case subjects (25.6%) and control subjects (24.4%) reported ever use of marijuana (adjusted odds ratio, 0.9; 95% confidence interval, 0.6-1.3). There were no trends in risk observed with increasing duration or average frequency of use or time since first or last use. No subgroup defined by known or suspected OSCC risk factors (age, cigarette smoking, alcohol consumption, and genetic polymorphisms) showed an increased risk. Marijuana use was not associated with OSCC risk in this large, population-based study.

A peek into Pandora's box: the medical excuse marijuana controversy

The smoking of marijuana for medicinal applications is a volatile and difficult issue for the medical and regulatory communities which has reached the forefront of discussions of public policy. Any consideration of this issue must take into account the substantial toxicity, impurity, and morbidity associated with marijuana use. Several states have passed ballot initiatives or legislation that allow a medical excuse for possession of marijuana. These initiatives bypass the Food and Drug Administration process of proving safety and efficacy, and they have created serious regulatory dilemmas for state regulatory boards. Several examinations of the issue have consistently drawn question to the validity of smoking an impure substance while voicing concern for the well being of patients in need. The historical, social, medical, and legal issues are examined.

Respiratory health effects of cannabis: position statement of the Thoracic Society of Australia and New Zealand

Both the gaseous and the particulate phases of tobacco and cannabis smoke contain a similar range of harmful chemicals. However, differing patterns of inhalation mean that smoking a 'joint' of cannabis results in exposure to significantly greater amounts of combusted material than with a tobacco cigarette. The histopathological effects of cannabis smoke exposure include changes consistent with acute and chronic bronchitis. Cellular dysplasia has also been observed, suggesting that, like tobacco smoke, cannabis exposure has the potential to cause malignancy. These features are consistent with the clinical presentation. Symptoms of cough and early morning sputum production are common (20-25%) even in young individuals who smoke cannabis alone. Almost all studies indicate that the effects of cannabis and tobacco smoking are additive and independent. Public health education should dispel the myth that cannabis smoking is relatively safe by highlighting that the adverse respiratory effects of smoking cannabis are similar to those of smoking tobacco, even although it remains to be confirmed that smoking cannabis alone leads to the development of chronic lung disease.

Delta 9-tetrahydrocannabinol disrupts mitochondrial function and cell energetics

We have observed rapid and extensive depletion of cellular energy stores by Delta(9)-tetrahydrocannabinol (THC) in the pulmonary transformed cell line A549. ATP levels declined dose dependently with an IC(50) of 7.5 microg/ml of THC after 24-h exposure. Cell death was observed only at concentrations >10 microg/ml. Studies using JC-1, a fluorescent probe for mitochondrial membrane potential, revealed diminished mitochondrial function at THC concentrations as low as 0.5 microg/ml. At concentrations of 2.5 or 10 microg/ml of THC, a decrease in mitochondrial membrane potential was observed as early as 1 h after THC exposure. Mitochondrial function remained diminished for at least 30 h after THC exposure. Flow cytometry studies on cells exposed to particulate smoke extracts indicate that JC-1 red fluorescence was fivefold lower in cells exposed to marijuana smoke extract relative to cells exposed to tobacco smoke extract. Comparison with a variety of mitochondrial inhibitors demonstrates that THC produced effects similar to that of carbonyl cyanide p-trifluoromethoxyphenylhydrazone, suggesting uncoupling of electron transport. Loss of red JC-1 fluorescence by THC was suppressed by cyclosporin A, suggesting mediation by the mitochondrial permeability transition pore. This disruption of mitochondrial function was sustained for at least 24 h after removal of THC by extensive washing. These results suggest that exposure of the bronchopulmonary epithelium to THC may have important health and physiological consequences.

Beyond the theoretical rhetoric: a proposal to study the consequences of drug legalization

Drug legalization is a frequently-debated drug control policy alternative. It should come as little surprise, therefore, that the arguments in favor of both legalization and prohibition have resulted in a conceptual stalemate. While theoretical deliberations are unquestionably valuable, they seem to have propelled this particular issue to its limit. To date, no works have suggested any empirical studies that might test the framework and potential consequences of drug legalization. In the current study, the arguments surrounding the drug legalization debate are synthesized into a proposal for future research. Such a proposal illustrates that the core elements surrounding drug legalization are not only testable, but that the time may be right to consider such an empirical effort.

Airway inflammation in young marijuana and tobacco smokers

Forty healthy young subjects, ages 20 to 49 yr, underwent videobronchoscopy, mucosal biopsy, and bronchial lavage to evaluate the airway inflammation produced by habitual smoking of marijuana and/or tobacco. Videotapes were graded in a blinded manner for central airway erythema, edema, and airway secretions using a modified visual bronchitis index. The bronchitis index scores were significantly higher in marijuana smokers (MS), tobacco smokers (TS), and in combined marijuana/tobacco smokers (MTS), than in nonsmokers (NS). As a pathologic correlate, mucosal biopsies were evaluated for the presence of vascular hyperplasia, submucosal edema, inflammatory cell infiltrates, and goblet cell hyperplasia. Biopsies were positive for two of these criteria in 97% of all smokers and for three criteria in 72%. By contrast, none of the biopsies from NS exhibited greater than one positive finding. Finally, as a measure of distal airway inflammation, neutrophil counts and interleukin-8 (IL-8) concentrations were determined in bronchial lavage fluid. The percentage of neutrophils correlated with IL-8 levels and exceeded 20% in 0 of 10 NS, 1 of 9 MS, 2 of 9 TS, and 5 of 10 MTS. We conclude that regular smoking of marijuana by young adults is associated with significant airway inflammation that is similar in frequency, type, and magnitude to that observed in the lungs of tobacco smokers.

Marijuana. Respiratory tract effects

Daily marijuana smoking has been clearly shown to have adverse effects on pulmonary function and produce respiratory symptomatology (cough, wheeze, and sputum production) similar to that of tobacco smokers. Based on the tobacco experience, decrements in pulmonary function may be predictive of the future development of chronic obstructive pulmonary disease (COPD). However, in the absence of alpha-1-antitrypsin deficiency, the habitual marijuana-only smoker would likely have to smoke 4-5 joints per day for a span of at least 30 yr in order to develop overt manifestations of COPD. The mutagenic/carcinogenic properties of marijuana smoke are also well-established. The potential for induction of laryngeal, oropharyngeal, and possibly bronchogenic carcinoma from marijuana has been documented by several case reports and observational series. Despite this, a relative risk ratio for the development of these tumors has not yet been quantified. Based on a higher frequency of case reports for upper airway cancer compared to bronchogenic carcinoma, marijuana smoking may have a more deleterious effect on the upper respiratory tract. However, this hypothesis remains speculative at best, pending confirmation by longitudinal studies.

The phenomenon of abusable psychotropic use among North American youth

Abusable psychotropic use can, and does, affect all North American youth, either directly or indirectly, regardless of age, gender, culture, ethnic background, education, race, or socioeconomic status. Over the last decade, the morbidity and mortality associated with abusable psychotropic use among youth have become staggering. A current overview of the phenomenon of abusable psychotropic use among youth in North America, including the use of alcohol, cannabis, cocaine, LSD, nicotine, and polyabusable psychotropic use, is presented with attention to the expanding role of clinical pharmacologists in relation to both prevention and treatment. The Mega Interactive Model of Abusable Psychotropic Use Among Youth is presented as a heuristic device to assist clinical pharmacologists, and other health care providers, in addressing the multifactorial interactive aspects of this complex phenomenon as observed in the pediatric age group. In this regard, attention is given to the interaction of the Abusable Psychotropic Dimension, including the Abusable Psychotropic Variables (e.g., pharmacokinetics, abuse potential) and Pattern of Use Variables (e.g., social use, abuse, compulsive use), with the Young Person, Societal, and Time Dimensions.

Pneumothorax in polysubstance-abusing marijuana and tobacco smokers: three cases

Three patients are reported who suffered spontaneous pneumothorax, each of whom also had a history of daily marijuana and tobacco use. The patients ranged in age from 24 to 37 years, had smoked marijuana on a daily basis for 10 to 14 years, and had 11 to 50 pack-year tobacco-smoking histories. Marijuana may predispose to pneumothorax both by accelerating tobacco-induced lung disease, and by the frequent performance of the Valsalva maneuver during marijuana smoking. Although there is an association between pneumothorax and heavy tobacco use, an association with chronic daily marijuana use has not previously been reported.

No increase in carcinogen-DNA adducts in the lungs of monkeys exposed chronically to marijuana smoke

Rhesus monkeys exposed to marijuana smoke either 7 or 2 days/weeks (HI and LO groups, respectively), or ethanol-extracted marijuana smoke for 7 days/week (EM) or sham treatment (SH) for 1 year were sacrificed 7 months following the last exposure. Pulmonary levels of carcinogen-DNA adducts were determined. Although mean or median adduct levels were not statistically different, 15 of 22 adduct measures were highest in the EM group and lowest 12 of 22 times in the SH group. The levels of aromatic carcinogen-DNA adducts seem no higher in the lungs of animals exposed to marijuana smoke than in untreated animals. Ethanol-extracted marijuana may have effects greater than marijuana itself.

Reinforcing and subjective effects of oral delta 9-THC and smoked marijuana in humans

The reinforcing and subjective effects of oral delta-9-tetrahydrocannabinol (THC) and smoked marijuana were studied in two groups of regular marijuana users. One group (N = 10) was tested with smoked marijuana and the other (N = 11) with oral THC. Reinforcing effects were measured with a discrete-trial choice procedure which allowed subjects to choose between the self-administration of active drug or placebo on two independent occasions. Subjective effects and heart rate were measured before and after drug administration. Smoked active marijuana was chosen over placebo on both choice occasions by all subjects. Similarly, oral THC was chosen over placebo on both occasions by all but one subject. Both active drug treatments produced qualitatively and quantitatively similar subjective effects, and both significantly increased heart rate, although the time course of effects differed substantially between the two treatments. The results demonstrate that both smoked marijuana and oral THC can serve as positive reinforcers in human subjects under laboratory conditions. The experimental paradigm used here should prove useful for identifying factors that influence the self-administration of marijuana and other cannabinoids by humans.

Marijuana exposure and pulmonary alterations in primates

As part of a large multidisciplinary study, we examined lungs from 24 periadolescent male rhesus monkeys that were sacrificed seven months after daily marijuana smoke inhalation of 12 months duration. Animals were divided into four exposure groups: A) high-dose (one marijuana cigarette 7 days/week), B) low-dose (one marijuana cigarette 2 days/week and sham smoke 5 days/week), C) placebo (one extracted marijuana cigarette 7 days/week), and D) sham (sham smoke 7 days/week). Lungs, removed intact, were formalin inflated, sectioned and examined. Several pathological alterations, including alveolitis, alveolar cell hyperplasia and granulomatous inflammation, were found with higher frequency in all cigarette-smoking groups. Other alterations, such as bronchiolitis, bronchiolar squamous metaplasia and interstitial fibrosis, were found most frequently in the marijuana-smoking groups. Alveolar cell hyperplasia with focal atypia was seen only in the marijuana-smoking animals. These changes represent mostly early alterations of small airways. Additional follow-up studies are needed to determine their long-term prognostic significance.

Marijuana smoking and carcinoma of the tongue. Is there an association?

There is considerable theoretical evidence that marijuana should be carcinogenic. However, most reviews have found no direct evidence of chronic marijuana smoking causing lung cancer. Some recent reports implicate marijuana smoking as a cause of cancer of the upper aerodigestive tract, though most of the subjects were exposed to other, possibly confounding, etiologic factors, namely tobacco and alcohol. We report two cases of squamous cell carcinoma of the tongue in men who chronically smoked marijuana but had no other risk factors. The totality of cases may point to a predilection of marijuana smoke for carcinogenesis in the upper aerodigestive tract. This correlates with nonmalignant effects and may be related to a different method of smoking marijuana compared with tobacco.